Lighting arrangement



`lune 7, 1966 E. O. SElTZ ETAL LI GHT ING ARRANGEMENT Filed May 6, 1965United States Patent O 3,255,342 LIGHTING ARRANGEMENT Ernst 0. Seitz,Hans Ulrich Klippert, and Wolfgang Friedl, Hanau am Main, Germany,assignors to Quarzlampen Gesellschaft m.b.H., Hanau am Main, GermanyFiled May 6, 1963, Ser. No. 278,060

Claims priority, applicatiolllGerrnany, May 4, 1962,

5 Claims. (Cl. 240-1.4)

The present invention relates to a lighting arrangement and, moreparticularly, to a lighting arrangement such as is used for illuminatingsurgical operating tables and the like.

Lighting arrangements of this kind usually comprise a light source and areflector for concentrating the light rays emitted by the light source.The reflector usually has a concave light-reflecting surface andadjacent thereto a shielding arrangement is provided, with the lightsource such as a light bulb interposed between the reflector and theshielding arrangement.

C onventionally, the shielding arrangement comprises three parallelplates each of which serves a different purpose.

The plate nearest the reflector and light bulb has heat-absorbingproperties. This is important because only a small portion of the energysupplied to the light source such as a light bulb will be converted intovisible light, while the major portion of the energy will be directlyconverted into heat. For instance, the optical effectiveness of anelectric light bulb is only about 4% so that about 96% of the energysupplied to the light bulb will be emitted as heat radiation,particularly infrared radiation. While it is desired to concentrate thevisible light towards a portion of the operating table, it is importantto prevent as much as possible of the heat radiation from reaching thearea `of the operating table. The heat-absorbing plate or sheet willserve to absorb most of the radiant heat energy so that the same willnot pass further towards the operating table.

The second plate or sheet conventionally consists of cathedral glass,i.e., of a sheet of glass having an unpolished or uneven surface whichwill scatter and diffuse the-visible light rays passing therethrough.This is important in order to prevent blinding of personnel and patientby direct visibility of the light source. The sheet lof cathedral glassis translucent but not transparent. Furthermore, the sheet serves foreliminating shadows and/or the reflection of the light source in theoperating area.

Finally, the third sheet which is nearest to the operating table andfurthest distant from the reflector and the light source serves as ashielding member and will prevent the dropping of any portion of thelighting arrangement, for instance, `of glass splinters, into theoperating area. This shielding member in conventional arrangementspreferably consists of transparent synthetic plastic material, forinstance, of the type known as Plexiglas, i.e., a thermoplastic poly(methyl methacrylate)type polymer.

However, certain disadvantages are connected with such conventionalarrangements. These disadvantages include the necessity of arranging arelatively large number of sheets or plates such as described abovebetween the light source and the area which is to be illuminated andthereby a considerable portion of the visible light rays will not reachthe operating area or the like. Furthermore, notwithstanding thearrangement of, for instance, all these three sheets described above,there will still be a marked and considerable heat radiation into theoperating area due to the fact that al1 heat-absorbing materials are toa limited degree permeable for heat 3,255,342 Patented June 7, 1966radiation and because after using the lighting arrangement for aprolonged period of time, the temperature of the heat-absorbing platewill rise to such an extent that this plate will act as a source ofsecondary heat radiation.

It is therefore an object of the present invention to overcome the abovediscussed difficulties and disadvantages connected with conventionallighting arrangements of the type described.

It is a further object of the present invention to provide a lightingarrangement which will allow a limited area -to be illuminated with ahigh proportion of the visible light rays emitted from the light sourcewhile at the same time keeping the illuminated area substantially freeof heat radiation.

Other objects and advantages of the present invention will becomeapparent from a further reading of the description and of the appendedclaims.

With the above and other objects in View, the present combination, alight source having opposite sides and adapted to ernit visible lightand infrared radiation from one of the opposite sides, reflector meanslocated adjacent one of the opposite sides of the light source in thepath of the radiation emitted therefrom for substantially reflecting theemitted visible light while permitting passage of at least a portion ofthe infrared radiation through the reflector means, and translucentshielding means arranged across the path of the reflected light fordiffusing the reflected light passing therethrough.

According to a preferred embodiment, the present invention includes alighting arrangement for an operating table and the like, comprising, incombination, a reflector having a concave, visible light-reflectingsurface and adapted for the passage of infrared radiation therethrough,a sheet of light-permeable synthetic plastic material arranged spacedfrom the reflector in the path of the visible light reflected by theconcave lightareflecting surface, the sheet having opposite surfaces,the opposite surface further distant from the reflector havinglight-diffusing properties, an infrared radiation reflecting layer beinglocated on the other of the opposite surfaces, and a light sourceinterposed between the concave surface of vthe reflector and thelight-permeable sheet, the light source being adapted to emit visiblelight and infrared radiation in the direction towards the reflector,whereby of the radiation emitted by the light source substantially onlydiffused visible light will pass through the sheet of light-permeablesynthetic plastic material.

Thus, laccording to the present invention, improved lighting and reducedheat radiation into the illuminated area are accomplished withoutrequiring any change in the light source and the general mode ofoperation of the lighting arrangement. This is achieved by increasingthe proportion of the visible light reaching the operating area or thelike, and/or reducing the amount of infrared radiation reaching saidarea.

According to preferred embodiments of the present invention, severalmeans for achieving this result are combined. However, as will be seenhereinbelow, any one of these means taken alone will also result in aconsiderable improvement of the lighting effect.

According to one of the features of the present invention, the reflectorof the lighting arrangement is a socalled col light concave mirror whichis known per se in the art. The term cold-light mirror denotes anoptical surface which will substantially reflect visible lightradiation, while long wave heat radiation will substantially passthrough the same. Such mirrors are usually arranged in accordance withan interference filter principle. They can be produced by vapordeposition of several very thin layers of non-absorbing dielectricmaterials with alternatingly different indices of re-v fraction. Thesemi-spherical end portion of light bulbs used for illuminatingoperating tables and the like are generally provided with asubstantially light and infrared radiation impermeable mirror layer sothat the major portion of the heat radiation emanating from the lightbulb will not be directed towards the area which is to be illuminatedbut towards the reflecting surface of the reflector. If the reflector isof the cold-light hollow mirror type, then most of the infraredradiation emanating from the light bulb is directed towards thereflector and will pass through the same without being reflected. Only aminor portion of the infrared radiation emitted by the light bulb willthen have to be prevented from reaching the illuminated area byinterposition of a heatabsorbing sheet or heat filter. Due to therelatively small amount of infrared radiation which will thus still haveto be absorbed by the heat filter or infrared radiation-absorbing sheet,the latter may be of somewhat lesser heat-absorbing effectiveness andconsequently can be of greater permeability for visible light rays sothat a greater portion of the visible light rays emitted from the lightsource and reflected by the reflector will pass therethrough towards thearea which is to be illuminated. In certain cases it is even possible byusing a cold-light mirror reflector to eliminate the heat filter orheatabsorbing sheet altogether.

A second feature of the present invention will be found in the provisionof at least one infrared radiationreflecting mirror in the shieldingmember of the lighting arrangement. The infrared reflecting mirror isunderstood to be an optical surface which substantially permits thepassage therethrough of visible light rays and which, however, willsubstantially reflect heat radiation such as infrared radiation. Suchinfrared reflecting mirror may be formed as an interference filter byvapor deposition of several very thin layers of different dielectricmaterials with alternatingly differing indices of refraction. Byarranging one or more infrared mirrors in the paths of radiation afterthe same has passed through the heat-absorbing sheet or filter, it ispossible to reflect the major portion of the residual heat rays, such asinfrared rays, which have passed through or are emitted by theheat-absorbing sheet. By combining an infrared mirror as described abovewith a reflector formed as a cold-light mirror, and omitting theheat-absorbing sheet or heat filter, better results are obtained thanare obtainable with heat filters but without infrared mirrors andcold-light reflectors. This is due to the fact that the heat radiationis thus twice eliminated, namely, once by passing through the cold-lightreflector and the residual heat radiation by being reflected from the1nfrared mirror. Furthermore, due to elimination of the heat-absorbingsheet or plate, the same cannot become a secondary source of heatradiation.

According to a third feature of the present invention, either theheat-absorbing sheet, or the protective shielding plate or sheet ofsynthetic plastic material may be formed with a light scattering ordiffusing surface so as to achieve the so-called cathedral glass effectwithout requiring a separate sheet or plate for this purpose. In thismanner, two of the objects of conventional shielding arrangements areachieved with only one plate or sheet and thereby the number of sheetsof the shielding arrangement is reduced and the overall lightpermeability of the shielding arrangement is increased.

It will be clear from the foregoing that by combining -the threefeatures of the present invention which were discussed above, theobjects of the present invention will be achieved in a most effectivemanner, namely by xproviding a lighting arrangement which includes acold- Elight mirror reflector and a shielding arrangement which-consists of a single shield or ,plate having an infrared mirror on itsface directed towards the light source and reflector, and having alight-diffusing surface structure at the opposite surface, i.e., thesurface directed towards the area which is to be illuminated.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof,'will be best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a secional elevation of an embodiment of the presentinvention.

FIG. 2 is a sectional elevation of another embodiment of the presentinvention; and

FIG. 3 is a sectional elevation of a further embodiment of the presentinvention.

In all .three figures is shown a housing 1, a light bulb -2 as the lightsource, and it will be noted that the outer hemispherical portion 3 ofthe light bulb is mirrorplated so that light can be emitted only in thedirection toward the reflector 5, 15 or 25 and, furthermore, all figuresof the drawing show electric terminals 4 and wire connections from theterminals to bulb 2.

Referring now to the embodiment of the present invention illustrated inFIG. l, a reflector 5 is shown which is formed as a cold-light concavemirror. In Iother Words, the relatively short wave infrared radiationemitted by bulb 2 indicated by arrows and indicia IR will pass throughthe reflector without being reflected, while the visible light indicatedby arrows S will be reflected.

The shielding means comprise an inner or second sheet 6 oflight-permeable heat-absorbing material which is interposed between afirst light-permeable sheet 7 of synthetic plastic material and lightbulb 2. The outer surface of second sheet 6, i.e., the surface directedtowards first sheet 7 and towards the area to be illuminated is formedso as to give a cathedral glass effect, in other Words, so as to diffuselight so that the light which passes from bulb 2 to reflector 5 and fromthere through second sheet 6 and firs-t sheet 7 towards the area whichis to be illuminated will be diffused, will not give any sharp shadowsand so that the light source will not be visible when viewed from theilluminated area. Thus, a special plate for producing the cathedralglass effect is not required since this effect is achieved by thesuitably roughened lower surface of heat-absorbing plate 6. Theshielding arrangement according to FIG. l is of greater lightpermeability than the conventional 3-plate shielding arrangements.Furthermore, due to the fact that only relatively little infraredradiation reaches heat-absorbing sheet 6, the latter can be made thinnerand with better permeability for visible light than is possible inconventional arrangements in which a greater portion of the infraredradiation reaches the shielding arrangement. It will be noted that amajor portion of the infrared radiation passes in the direction ofarrows IR through the cold-light reflector and thus will not contact theshielding arrangement. According to FIG. 2, a conventional reflector 15is combined with a shielding arrangement according to the presentinvention. The conventional reflector reflects not only visible lightbut also infrared radiation.

The shielding arrangement again consists of two sheets or plates, namelyheat-absorbing plate or sheet 16 and plate or sheet 17 of syntheticplastic material. The lower face 18 of sheet 17 is unpolished or roughso as to give the cathedral glass effect of diffusing light passingtherethrough. The upper surface of plate 17 consists of infrared mirror19 which will reflect relatively long wave infrared radiation. Heatfilter or heat-absorbing sheet 16 is formed with infrared mirror 20 atits lower face which serves the purpose of reflecting relatively shortwave infrared radiation back towards bulb 2 and reflector 15.

According to the embodiment illustrated in FIG. 2, the shieldingarrangement again consists only of two plates or sheets and the specialplate conventionally used for obtaining the cathedral glass effects isomitted since the function of this plate, namely diffusion of t-he lightpassing therethrough, is achieved by surface portion 18 of sheet orplate 17. Heat radiation is absorbed in a conventional manner by sheetor plate 16. However, residual relatively short wave infrared primaryradiation which may pass through sheet 16 is reflected by the infraredmirror surface 20 and thus will not reach the area of illumination, forinstance the surgical operating area. Upon increase in the temperatureof heat absorbing sheet 16, relatively long wave infrared radiationformed thereby will-be reflected by infrared mirror 19 forming the uppersurface of sheet 17 and thus also will be prevent from reaching the areaof intended illumination.

According to the embodiment illustrated in FIG. 3, the reflector 25 isformed as concave cold-light mirror reflector.

The shielding arrangement consists of only a single sheet or plate,namely sheet 27 of synthetic material such as Plexiglas. Lower surface28 of sheet 27 is roughened so as to give the cathedral glass effect ofdiffusing light passing therethrough, while on t-he upper face of plate27 infrared mirror 29 is formed.

Visible light, emitted by light bulb 2 is reflected at reflector 25 andpasses through the shielding arrangement as indicated by arrow S. Shortwave infrared radiation emitted by light bulb 2 passes substantiallythrough coldlight reflector 25 as indicated by arrow IR, while anyreflected portion of infrared radiation which reaches plate or sheet 28will be reflected by infrared mirror 29, as indicated by arrow IR andthus eventually will reach again cold-light reflector 25 and passoutwardly through the same substantially as indicated by arrow IR.

Due to the fact that in this case the shiel-ding arrangement requiresonly a single sheet or plate, a relatively very large proportion of thevisible ilight emitted by bulb 2 will in fact reach the area intended tobe illuminated while, on the other hand, -only an insignificant amountof heat or infrared radiation will penetrate through the shieldingmember.

It is also possible to combine the features of the presentinventiondifferently from the manner in which these features werecombined in the illustrated embodiments, or alsoto use one or the otherfeature alone.

For instance, the cold-light concave mirror of FIG. 1 or the infraredmirror or mirrors of FIG. 2 may be utilized in a 3-sheet shieldingarrangement, whereby only heat radiation into the operating area or thelike is reduced without increasing the efficiency of visible lighttransmission. On the other hand, it is possible by just combining twofunctions of different sheets of the shielding arrangement in a singlesheet thereof to increase the efficiency of light transmission withoutreducing the transmission of heat or infrared radiation below -thevalues obtained with conventional devices of this type. However, it ispreferred to combine the three above described features of the presentinvention, for instance in the manner illustrated in FIG. 3.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types oflighting arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in alighting arrangement for an oper-ating table and the like, it is notlintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various `applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharac- -teristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired is to be secured by Letters Patentis:

1. In a lighting arrangement, in combination, a light source havingfirst and second opposite sides and adapted to emit visible light andinfrared radiation from said first and second opposite sides in a firstand second opposite direction, respectively; an opaque shielding meansarranged closely adjacent to and substantially commensurate in size tosaid first opposite side of said light source blocking passage ofdirectly emitted visible light and infrared radiation in said firstopposite direction; reflector means located adjacent said second of saidopposite sides of said light source in the path of said visible lightand infrared radiation emitted therefrom in said opposite direction,thereby substantially reflecting said emitted visible light in saidfirst opposite direction and past said opaque shielding means Whilepermitting passage of at least a portion of said infrared radiationthrough said reflector means in said second opposite direction; and atranslucent shielding and diffusing element arranged across the path ofsaid reflected light and carrying on one surface thereof an infraredradiation reflecting layer so as to substantially prevent passage ofsaid infrared radiation through said element while permitting saidreflectedl light to pass through the element and diffusing said lightthereby.

2. A lighting arrangement as defined in claim 1, wherein said reflectormeans is concave.

3. A lighting arrangement as defined in claim 1,

wherein said reflector means is concave and said translucent shieldingand diffusing element is a sheet of lightpermeable material.

4. A lighting arrangement as defined in claim 1, wherein said reflectormeans is concave and said translucent shielding and diffusing element isa sheet of light permeable synthetic plastic material.

S. A lighting arrangement as defined in claim 1, wherein said reflectormeans is concave and said translucent shielding and diffusing element isa sheet of light permeable synthetic plastic material having a secondsurface opposite said one surface, said second surface havinglight-diffusing properties.

References Cited by the Examiner UNITED STATES PATENTS 1,927,181 9/1933McRe-a 24U-41.15 2,006,839 7/1935 Moller 24U- 46.9 X 2,244,737 6/ 1941Stewart 240-4l.3 X 2,494,058 1/ 1950 Ries et al. 240-41.15 2,798,943 7/1957 Prideaux 240-47 3,120,352 2/1964 Akita et al. 88-113 X 3,149,9899/1964 Johnson 88--112 X 3,174,067 3/1965 Bahrs 240-47 EVON C. BLUNK,Primary Examiner.

NORTON ANSHER, I. F. PETERS,

Assistant Examiners.

1. IN A LIGHTING ARRANGEMENT, IN COMBINATION, A LIGHT SOURCE HAVINGFIRST AND SECOND OPPOSITE SIDES AND ADAPTED TO EMIT VISIBLE LIGHT ANDINFRARED RADIATION FROM SAID FIRST AND SECOND OPPOSITE SIDES IN A FIRSTAND SECOND OPPOSITE DIRECTION, RESPECTIVELY; AN OPAQUE SHIELDING MEANSARRANGED CLOSELY ADJACENT TO AND SUBSTANTIALLY COMMENSURATE IN SIZE TOSAID FIRST OPPOSITE SIDE OF SAID LIGHT SOURCE BLOCKING PASSAGE OFDIRECTLY EMITTED VISIBLE LIGHT AND INFRARED RADITION IN SAID FIRSTOPPOSITE DIRECTION; REFLECTOR MEANS LOCATED ADJACENT SAID SECOND OF SAIDOPPOSITE SIDES OF SAID LIGHT SOURCE IN THE PATH OF SAID VISIBLE LIGHTAND INFRARED RADIATION EMITTED THEREFROM IN SAID OPPOSITE DIRECTION,THEREBY SUBSTANTIALLY REFLECTING SAID EMITTED VISIBLE LIGHT IN SAIDFIRST OPPOSITE DIRECTION AND PAST SAID OPAQUE SHIELDING MEANS WHILEPERMITTING PASSAGE OF AT LEAST A PORTION OF SAID INFRARED RADIATIONTHROUGH SAID REFLECTOR MEANS IN SAID SECOND OPPOSITE DIRECTION; AND ATRANSLUENT SHIELDING AND DIFFUSING ELETHE VALUE OF THE REMAINDER IN SAIDFIRST-NEMED PARTIAL CARRYING ON ONE SURFACE SURFACE THEREOF AN INFRAREDRADIATION REFLECTING LAYER SO AS TO SUBSTANTIALLY PREVENT PASSAGE OFSAID INFRARED RADIATION THROUGH SAID ELEMENT WHILE PERMITTING SAIDREFLECTED LIGHT TO PASS THROUGH THE ELEMENT AND DIFFUSING SAID LIGHTTHEREBY.